This PR performs a small amount of cleanup after #618 based on the PR discussion. Specifically, it:

• Adds a new project_filter_from_projects function to the filters file, and makes project_filter fall back to that on the back end (we can discuss the names here, but doing it this way saved me touching any more code)
• Reverts the std::mem::take shenanigans in favor of cloning. Even though it clones one string per attached listener every 30 seconds, it's probably not going to cause a lot of memory overhead given that we drop the original shortly thereafter.